A siphon is a tube that moves liquid from a higher-elevation container to a lower-elevation container, driven by atmospheric pressure and gravity. Making a liquid flow downstream does not normally present much of a challenge; a siphon can do it even if a vertical barrier holds the higher container's liquid back, however. Consider, for example, a gasoline thief who siphons fuel from a car into a hand-carry gas tank; the wall of the gas tank above the fuel level becomes the vertical barrier in this case. Build your siphon for less illicit activities---transferring beverages from one container to another, for example, or demonstrating the properties of liquid dynamics to students.
- Skill level:
- Moderately Easy
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Things you need
- 2 shut-off valves
- Pipette bulb (optional)
Attach a shut-off valve to each end of your garden hose. They cost £1.30 each at your local garden store. Leave the stopcocks open for now.
Submerge the hose fully in the bottom container. To avoid air bubbles, submerge the hose vertically, inch by inch, until you have submerged both ends.
Close the stopcock of each shut-off valve. Lift one end of the hose out of the water and into the container above.
Orient the end of the hose in the higher container to point upward, and open its shut-off valve. Air bubbles escaping may indicate a poor seal and that the siphon might not work. An air bubble at the top of the siphon hose (i.e., the U-turn it makes at the top of the vertical barrier between the containers) will prevent the water from flowing through---if the bubble grows larger than the width of the hose.
If bubbles came out of the upper end of the hose during Step 4, remove the hose from the containers and grease the stopcocks for airproofing. Then start from the beginning again at Step 1.
Open both shut-off valves. The liquid should start flowing from the upper container to the lower.
Tips and warnings
- If access to the higher container prohibits opening the stopcock, insert the hose into the upper chamber, then suction out liquid. Though a pipette bulb could provide the necessary suction, it may not be wide enough for a garden hose.
- Keep the water level of the lower container below the water level of the higher container in order for water to flow down from the higher to lower. The siphon will stop flowing once the two levels reach the same point.
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